include/linux/tty_ldisc.h

   1 #ifndef _LINUX_TTY_LDISC_H
   2 #define _LINUX_TTY_LDISC_H
   3
   4 /*
   5  * This structure defines the interface between the tty line discipline
   6  * implementation and the tty routines.  The following routines can be
   7  * defined; unless noted otherwise, they are optional, and can be
   8  * filled in with a null pointer.
   9  *
  10  * int  (*open)(struct tty_struct *);
  11  *
  12  *      This function is called when the line discipline is associated
  13  *      with the tty.  The line discipline can use this as an
  14  *      opportunity to initialize any state needed by the ldisc routines.
  15  *
  16  * void (*close)(struct tty_struct *);
  17  *
  18  *      This function is called when the line discipline is being
  19  *      shutdown, either because the tty is being closed or because
  20  *      the tty is being changed to use a new line discipline
  21  *
  22  * void (*flush_buffer)(struct tty_struct *tty);
  23  *
  24  *      This function instructs the line discipline to clear its
  25  *      buffers of any input characters it may have queued to be
  26  *      delivered to the user mode process.
  27  *
  28  * ssize_t (*read)(struct tty_struct * tty, struct file * file,
  29  *                 unsigned char * buf, size_t nr);
  30  *
  31  *      This function is called when the user requests to read from
  32  *      the tty.  The line discipline will return whatever characters
  33  *      it has buffered up for the user.  If this function is not
  34  *      defined, the user will receive an EIO error.
  35  *
  36  * ssize_t (*write)(struct tty_struct * tty, struct file * file,
  37  *                  const unsigned char * buf, size_t nr);
  38  *
  39  *      This function is called when the user requests to write to the
  40  *      tty.  The line discipline will deliver the characters to the
  41  *      low-level tty device for transmission, optionally performing
  42  *      some processing on the characters first.  If this function is
  43  *      not defined, the user will receive an EIO error.
  44  *
  45  * int  (*ioctl)(struct tty_struct * tty, struct file * file,
  46  *               unsigned int cmd, unsigned long arg);
  47  *
  48  *      This function is called when the user requests an ioctl which
  49  *      is not handled by the tty layer or the low-level tty driver.
  50  *      It is intended for ioctls which affect line discpline
  51  *      operation.  Note that the search order for ioctls is (1) tty
  52  *      layer, (2) tty low-level driver, (3) line discpline.  So a
  53  *      low-level driver can "grab" an ioctl request before the line
  54  *      discpline has a chance to see it.
  55  *
  56  * long (*compat_ioctl)(struct tty_struct * tty, struct file * file,
  57  *                      unsigned int cmd, unsigned long arg);
  58  *
  59  *      Process ioctl calls from 32-bit process on 64-bit system
  60  *
  61  * void (*set_termios)(struct tty_struct *tty, struct ktermios * old);
  62  *
  63  *      This function notifies the line discpline that a change has
  64  *      been made to the termios structure.
  65  *
  66  * int  (*poll)(struct tty_struct * tty, struct file * file,
  67  *                poll_table *wait);
  68  *
  69  *      This function is called when a user attempts to select/poll on a
  70  *      tty device.  It is solely the responsibility of the line
  71  *      discipline to handle poll requests.
  72  *
  73  * void (*receive_buf)(struct tty_struct *, const unsigned char *cp,
  74  *                     char *fp, int count);
  75  *
  76  *      This function is called by the low-level tty driver to send
  77  *      characters received by the hardware to the line discpline for
  78  *      processing.  <cp> is a pointer to the buffer of input
  79  *      character received by the device.  <fp> is a pointer to a
  80  *      pointer of flag bytes which indicate whether a character was
  81  *      received with a parity error, etc. <fp> may be NULL to indicate
  82  *      all data received is TTY_NORMAL.
  83  *
  84  * void (*write_wakeup)(struct tty_struct *);
  85  *
  86  *      This function is called by the low-level tty driver to signal
  87  *      that line discpline should try to send more characters to the
  88  *      low-level driver for transmission.  If the line discpline does
  89  *      not have any more data to send, it can just return. If the line
  90  *      discipline does have some data to send, please arise a tasklet
  91  *      or workqueue to do the real data transfer. Do not send data in
  92  *      this hook, it may leads to a deadlock.
  93  *
  94  * int (*hangup)(struct tty_struct *)
  95  *
  96  *      Called on a hangup. Tells the discipline that it should
  97  *      cease I/O to the tty driver. Can sleep. The driver should
  98  *      seek to perform this action quickly but should wait until
  99  *      any pending driver I/O is completed.
 100  *
 101  * void (*dcd_change)(struct tty_struct *tty, unsigned int status)
 102  *
 103  *      Tells the discipline that the DCD pin has changed its status.
 104  *      Used exclusively by the N_PPS (Pulse-Per-Second) line discipline.
 105  *
 106  * int  (*receive_buf2)(struct tty_struct *, const unsigned char *cp,
 107  *                      char *fp, int count);
 108  *
 109  *      This function is called by the low-level tty driver to send
 110  *      characters received by the hardware to the line discpline for
 111  *      processing.  <cp> is a pointer to the buffer of input
 112  *      character received by the device.  <fp> is a pointer to a
 113  *      pointer of flag bytes which indicate whether a character was
 114  *      received with a parity error, etc. <fp> may be NULL to indicate
 115  *      all data received is TTY_NORMAL.
 116  *      If assigned, prefer this function for automatic flow control.
 117  */
 118
 119 #include <linux/fs.h>
 120 #include <linux/wait.h>
 121
 122
 123 /*
 124  * the semaphore definition
 125  */
 126 struct ld_semaphore {
 127         long                    count;
 128         raw_spinlock_t          wait_lock;
 129         unsigned int            wait_readers;
 130         struct list_head        read_wait;
 131         struct list_head        write_wait;
 132 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 133         struct lockdep_map      dep_map;
 134 #endif
 135 };
 136
 137 extern void __init_ldsem(struct ld_semaphore *sem, const char *name,
 138                          struct lock_class_key *key);
 139
 140 #define init_ldsem(sem)                                         \
 141 do {                                                            \
 142         static struct lock_class_key __key;                     \
 143                                                                 \
 144         __init_ldsem((sem), #sem, &__key);                      \
 145 } while (0)
 146
 147
 148 extern int ldsem_down_read(struct ld_semaphore *sem, long timeout);
 149 extern int ldsem_down_read_trylock(struct ld_semaphore *sem);
 150 extern int ldsem_down_write(struct ld_semaphore *sem, long timeout);
 151 extern int ldsem_down_write_trylock(struct ld_semaphore *sem);
 152 extern void ldsem_up_read(struct ld_semaphore *sem);
 153 extern void ldsem_up_write(struct ld_semaphore *sem);
 154
 155 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 156 extern int ldsem_down_read_nested(struct ld_semaphore *sem, int subclass,
 157                                   long timeout);
 158 extern int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass,
 159                                    long timeout);
 160 #else
 161 # define ldsem_down_read_nested(sem, subclass, timeout)         \
 162                 ldsem_down_read(sem, timeout)
 163 # define ldsem_down_write_nested(sem, subclass, timeout)        \
 164                 ldsem_down_write(sem, timeout)
 165 #endif
 166
 167
 168 struct tty_ldisc_ops {
 169         int     magic;
 170         char    *name;
 171         int     num;
 172         int     flags;
 173
 174         /*
 175          * The following routines are called from above.
 176          */
 177         int     (*open)(struct tty_struct *);
 178         void    (*close)(struct tty_struct *);
 179         void    (*flush_buffer)(struct tty_struct *tty);
 180         ssize_t (*read)(struct tty_struct *tty, struct file *file,
 181                         unsigned char __user *buf, size_t nr);
 182         ssize_t (*write)(struct tty_struct *tty, struct file *file,
 183                          const unsigned char *buf, size_t nr);
 184         int     (*ioctl)(struct tty_struct *tty, struct file *file,
 185                          unsigned int cmd, unsigned long arg);
 186         long    (*compat_ioctl)(struct tty_struct *tty, struct file *file,
 187                                 unsigned int cmd, unsigned long arg);
 188         void    (*set_termios)(struct tty_struct *tty, struct ktermios *old);
 189         unsigned int (*poll)(struct tty_struct *, struct file *,
 190                              struct poll_table_struct *);
 191         int     (*hangup)(struct tty_struct *tty);
 192
 193         /*
 194          * The following routines are called from below.
 195          */
 196         void    (*receive_buf)(struct tty_struct *, const unsigned char *cp,
 197                                char *fp, int count);
 198         void    (*write_wakeup)(struct tty_struct *);
 199         void    (*dcd_change)(struct tty_struct *, unsigned int);
 200         int     (*receive_buf2)(struct tty_struct *, const unsigned char *cp,
 201                                 char *fp, int count);
 202
 203         struct  module *owner;
 204
 205         int refcount;
 206 };
 207
 208 struct tty_ldisc {
 209         struct tty_ldisc_ops *ops;
 210         struct tty_struct *tty;
 211 };
 212
 213 #define TTY_LDISC_MAGIC 0x5403
 214
 215 #define LDISC_FLAG_DEFINED      0x00000001
 216
 217 #define MODULE_ALIAS_LDISC(ldisc) \
 218         MODULE_ALIAS("tty-ldisc-" __stringify(ldisc))
 219
 220 #endif /* _LINUX_TTY_LDISC_H */